Refractory clay for sliding nozzle and preparation method thereof

Abstract

The present invention provides a refractory mud for sliding water nozzle and a preparation method thereof, which belongs to the technical field of refractory materials, comprising the following steps: mixing aluminum hydroxide, water and phosphoric acid, heating reaction, after heating, adding boric acid, malic acid, tartaric acid and triethanolamine to continue the reaction, cooling to room temperature, filtering to obtain a modified phosphate binder; mixing zirconium powder and flake graphite, adding potassium chloride and sodium chloride to mix and stir, heating reaction in an inert gas, cooling, washing, and drying to obtain a nanocrystalline ZrC coated graphite material; ball milling and mixing fused magnesia, silicon powder and Al-Si alloy powder, adding modified magnesium aggregate, nanocrystalline ZrC coated graphite material and modified phosphate binder to mix, discharging and packaging to obtain refractory mud for sliding water nozzle. The present invention can improve the thermal shock resistance and slag erosion resistance of refractory mud for sliding water nozzle.

Description

Technical Field

[0001] The present invention relates to the technical field of refractory materials, in particular to refractory mud for sliding nozzles and a preparation method thereof. Background Art

[0002] The sliding nozzle is a key device used to precisely regulate the flow of molten steel during the continuous casting process. It ensures a balanced flow from the ladle to the tundish, enabling smoother and more controlled continuous casting operations. The sliding nozzle primarily consists of a drive mechanism, mechanical components, and refractory components (such as the upper and lower slides and the nozzle). Refractory clay plays a crucial role as a joint material, ensuring the stability and durability of the sliding nozzle.

[0003] Refractory clay is mainly composed of refractory powder, binder and additives, and its performance directly affects the service life and safety of the sliding gate. Excellent refractory clay should have good workability, volume stability, slag resistance, bonding strength and suitable sintering properties. Common types of refractory clay include high-alumina refractory clay, clay refractory clay, silica refractory clay, chrome corundum refractory clay, carbonaceous refractory clay, magnesia refractory clay, etc. Among them, high-alumina refractory clay is suitable for use in small and medium-sized ladles, but has poor corrosion resistance; chrome corundum refractory clay is expensive and has strong sintering properties, which makes it difficult to clean after use; carbon-containing refractory clay has become the most commonly used refractory clay due to its excellent corrosion resistance and easy cleaning. However, the carbon source in the carbon-containing refractory clay will penetrate into the molten steel during use, seriously affecting the composition, microstructure and performance of low-carbon steel.

[0004] Patent application publication number CN113956056B discloses a micro-expanded carbon-containing refractory mortar for sliding nozzles. The mortar's raw materials include fused mullite, kyanite, fused white corundum powder, calcined alumina powder, Guangxi white clay, flake graphite, solid aluminum dihydrogen phosphate, boron nitride, gum arabic powder, and carboxymethyl cellulose. While the resulting mortar possesses some oxidation resistance due to the addition of boron nitride, the flake graphite has a high specific surface area and is susceptible to agglomeration and oxidation within the refractory matrix at high temperatures, resulting in a decrease in the material's mechanical properties at high temperatures and a certain impact on its thermal shock resistance.

[0005] Therefore, it is necessary to provide a refractory clay for sliding nozzle and a preparation method thereof to solve the problems existing in the above-mentioned prior art. Summary of the Invention

[0006] In view of this, the present invention provides a refractory clay for a sliding nozzle and a preparation method thereof, which can improve the thermal shock resistance and slag erosion resistance of the refractory clay for the sliding nozzle.

[0007] To achieve the above object, the present invention provides a method for preparing refractory clay for sliding nozzle, comprising the following steps:

[0008] S1. Mix aluminum hydroxide, water and phosphoric acid, heat to react, add boric acid, malic acid, tartaric acid and triethanolamine after heating, continue reaction, cool to room temperature, and filter to obtain a modified phosphate binder;

[0009] S2. Mixing zirconium powder and flake graphite, adding potassium chloride and sodium chloride, stirring, heating to react in an inert gas, cooling, washing, and drying to obtain a nanocrystalline ZrC coated graphite material;

[0010] S3. The fused magnesia, silicon powder and Al-Si alloy powder are ball-milled and mixed, and modified magnesium aggregate, nanocrystalline ZrC coated graphite material and modified phosphate binder are added and mixed evenly, and the materials are discharged and packaged to obtain refractory mud for sliding nozzle.

[0011] The present invention prepares a modified phosphate binder to enhance the overall bonding strength. Tartaric acid, malic acid, and triethanolamine are used as modifiers. Organic acids and their derivatives can introduce carboxyl groups and hydroxyl groups to generate cross-linking reactions with molecules in the phosphate binder. The added organic acid provides H+ and also consumes free hydroxyl groups. The hydroxyethyl group of the triethanolamine and the boric acid in the original binder can form a stable complex, further enhancing the thermal stability of the modified phosphate binder. In addition, the reduction in hydroxyl activity promotes phosphate bonding, thereby enhancing the bonding strength of the binder, obtaining high cohesion and high adhesion, improving the overall bonding strength, and thus improving the overall mechanical strength.

[0012] The present invention utilizes a molten salt method to synthesize ZrC nanoparticles on the surface of flake graphite using zirconium powder as a zirconium source, resulting in a nanocrystalline ZrC-coated graphite material. During the preparation process, the potassium chloride and sodium chloride used melt at a relatively low temperature to form a liquid phase. Zirconium atoms / ions diffuse uniformly across the surface of the flake graphite in the molten salt medium, forming a uniformly structured and evenly distributed ZrC coating. The formation of the ZrC coating effectively reduces the carbon content of the graphite. In air or an oxidizing atmosphere, the zirconium carbide formed on the graphite surface is first oxidized to form a protective zirconium oxide layer, effectively preventing further oxidation of the material. Furthermore, the use of flake graphite as a carbon source leverages its excellent thermal conductivity, thermal shock resistance, and corrosion resistance, as well as its non-wetting properties with steel slag. This results in excellent resistance to steel slag penetration and erosion, preventing carbon from penetrating into molten steel during use, which could seriously affect the composition, microstructure, and performance of the mild steel. The ZrO2 crystal structure exhibits high thermal stability, resisting physical stress caused by temperature fluctuations, thereby improving the thermal shock resistance of the refractory material. In addition, ZrO2 will expand in volume during the phase change process, which helps to fill microcracks and thus increase the toughness and thermal shock resistance of the refractory material.

[0013] The present invention introduces Al-Si alloy powder as a metal additive into the unfired magnesia refractory material. The Al-Si alloy powder is oxidized into Al2O3 at high temperature, forming a dense surface layer on its surface, further inhibiting the oxidation of metallic Al. The outer Al2O3 layer can react with the surrounding MgO to form MgAl2O4, which can better resist thermal shock and slag erosion, and significantly improve the slag erosion resistance of the overall refractory clay material.

[0014] Optionally, the heating reaction time in step S1 is 30-40 minutes, the temperature is 65-75° C., the temperature after heating is 90° C., and the reaction time is continued for 40-60 minutes.

[0015] Optionally, the mixing and stirring time in step S2 is 15-20 minutes, the heating reaction temperature is 950-1000° C. and the time is 3-4 hours, and the drying temperature is 110-120° C. and the time is 10-12 hours.

[0016] Optionally, in step S2, potassium chloride and sodium chloride are premixed for 15 minutes before being added, and the mass ratio of potassium chloride to sodium chloride is 1:1; the inert gas is argon, the reagent used for washing is a hydrochloric acid solution with a volume concentration of 30%, and the number of washing times is 3 to 5 times.

[0017] The premixing of potassium chloride and sodium chloride in the present invention forms a uniform molten salt medium, which facilitates the reaction of zirconium powder and flake graphite at high temperatures and promotes the uniform formation of a nanocrystalline ZrC coating. Hydrochloric acid washing is used to remove salt impurities remaining after the high-temperature reaction, ensuring the purity of the final product.

[0018] Optionally, in step S3, modified magnesium aggregate is also added when the nanocrystalline ZrC coated graphite material and the modified phosphate binder are added.

[0019] Optionally, the modified magnesium aggregate is prepared by mixing high-purity magnesia powder and a mixed aqueous solution of citric acid-glucosamine hydrochloride for 3-5 minutes, adding microsilica powder and mixing for 5-10 minutes, and curing at 200° C. for 24 hours.

[0020] The present invention uses magnesia and silica powder as starting materials and citric acid and glucosamine hydrochloride as binders to prepare modified magnesium aggregate coated with silica powder. Amino groups bind to oxygen vacancies on the surface of the magnesia powder, glucosamine hydrochloride cross-links with citric acid, and amino groups form hydrogen bonds with Si-OH groups on the surface of the silica powder, thereby forming a coating layer that better disperses silicon in the matrix. The modified magnesium aggregate is introduced into refractory clay, and the silicon coating layer is converted into a protective ceramic layer of Si3N4, SiC, or Mg2SiO4 around the magnesia powder at high temperatures. The ceramic layer is evenly dispersed in the matrix, improving the thermal shock resistance and compressive strength of the overall material. The thermal expansion coefficient of these ceramic layers is lower than that of MgO, resulting in micro-gaps between the ceramic layer and the aggregate. Silicon is converted into a whisker ceramic phase in the micro-gaps, which helps to disperse stress and further improve the crack resistance and stability of the overall material in a high-temperature environment.

[0021] Optionally, the mass concentration of the citric acid-glucosamine hydrochloride mixed aqueous solution is 50%, and the mass ratio of citric acid to glucosamine hydrochloride is 1:1.

[0022] In the process of preparing the modified magnesium aggregate of the present invention, citric acid and glucosamine hydrochloride are used as binders. Citric acid forms a complex with magnesium ions in an aqueous solution. Glucosamine hydrochloride and citric acid work together to enhance the bonding effect and promote the stable attachment of silicon powder to the surface of magnesium sand powder.

[0023] Optionally, in step S3, the fused magnesia, silicon powder and Al-Si alloy powder are mixed in a ball mill for 3 to 5 minutes, placed in a strong mixer, and modified magnesium aggregate, nanocrystalline ZrC coated graphite material and modified phosphate binder are added and mixed for 15 to 20 minutes. After stirring evenly, the material is discharged and packaged to obtain refractory mud for sliding nozzle.

[0024] Optionally, the discharged material in step S3 is packaged and sealed in a packaging bag with a plastic lining.

[0025] The packaging of the present invention is sealed in a packaging bag with a plastic lining to achieve a moisture-proof effect.

[0026] Optionally, the refractory mud for the sliding nozzle includes the following raw materials in parts by mass: 25-85 parts of fused magnesia, 1-9 parts of silicon powder, 2-4 parts of Al-Si alloy powder, 35-60 parts of modified magnesium aggregate, 2-5 parts of nanocrystalline ZrC coated graphite material and 3-5 parts of modified phosphate binder;

[0027] The modified magnesium aggregate includes the following raw materials in parts by mass: 70 parts of high-purity magnesia powder, 2-10 parts of a mixed aqueous solution of citric acid-glucosamine hydrochloride, and 2-10 parts of microsilica powder; the modified phosphate binder includes the following raw materials in parts by mass: 6 parts of aluminum hydroxide, 30 parts of phosphoric acid, 0.4-0.6 parts of boric acid, 0.5-1 parts of malic acid, 0.1-0.3 parts of tartaric acid, and 0.5-1 parts of triethanolamine.

[0028] The present invention adopts the above-mentioned mass fraction matching ratio, which can better improve the comprehensive performance of the refractory clay for the sliding nozzle finally obtained, and the Al-Si alloy powder is controlled at 2 to 4 mass parts to exhibit higher mechanical properties, thermal shock resistance and slag resistance, avoiding the volume expansion caused by the formation of ceramic phase due to excessive alloy powder, thereby reducing the density of the refractory material.

[0029] The above technical solution of the present invention includes at least the following beneficial effects:

[0030] 1. This invention modifies a phosphate binder with tartaric acid, malic acid, and triethanolamine to promote intermolecular crosslinking and enhance bonding strength. The organic acid provides hydrogen atoms (H+) and consumes free hydroxyl groups. Triethanolamine forms a stable complex with boric acid, enhancing thermal stability and reducing hydroxyl activity, further promoting phosphate bonding. Ultimately, this enhances the binder's cohesion and adhesion, thereby improving overall mechanical strength.

[0031] 2. This invention utilizes a molten salt method to synthesize a nanocrystalline ZrC coating on the surface of flake graphite. Zirconium powder is used as the zirconium source, and potassium chloride and sodium chloride serve as the molten salt medium. This promotes the uniform diffusion of zirconium atoms and ions, forming a ZrC coating. This coating effectively reduces the carbon content of the graphite and forms a protective zirconium oxide layer in an oxidizing atmosphere, preventing further oxidation. The excellent thermal conductivity, thermal shock resistance, and corrosion resistance of flake graphite, as well as its non-wetting properties with steel slag, provide the material with excellent resistance to steel slag penetration. ZrO2, with its high thermal stability and volume expansion during phase transition, can improve the thermal shock resistance and toughness of the refractory material.

[0032] 3. The present invention adds Al-Si alloy powder to the magnesia refractory material. The generated Al2O3 layer inhibits the oxidation of metal Al and reacts with MgO to form MgAl2O4, thereby enhancing the thermal shock resistance and slag erosion resistance of the refractory material. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention. All other embodiments obtained by ordinary technicians in this field based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0034] Example 1

[0035] Add 6 parts of aluminum hydroxide to a three-necked flask, then add 80 mL of water and start the stirrer, heat in a water bath to 75°C, add 30 parts of phosphoric acid and react for 30 minutes, adjust the temperature to 90°C, add 0.4 parts of boric acid, 1 part of malic acid, 0.2 parts of tartaric acid and 1 part of triethanolamine and continue to react for 60 minutes, cool to room temperature and filter to obtain a modified phosphate binder.

[0036] 5 parts of zirconium powder and 15 parts of flake graphite were mixed in an alumina mortar for 15 minutes, and then 30 parts of potassium chloride and sodium chloride (the mass ratio of potassium chloride to sodium chloride is 1:1) pre-mixed for 15 minutes were added and stirred for 20 minutes. The mixture was heated to 1000°C in flowing argon for 3 hours. After the furnace was completely cooled, it was washed 5 times with a hydrochloric acid solution with a volume concentration of 30%, and then dried in a drying oven at 110°C for 12 hours to obtain nanocrystalline ZrC coated graphite material.

[0037] 70 parts of high-purity magnesia powder and 8 parts of a 50% mass concentration of citric acid-glucosamine hydrochloride mixed aqueous solution (the mass ratio of citric acid and glucosamine hydrochloride is 1:1) are added to a blender and mixed for 5 minutes, followed by adding 10 parts of microsilica powder and mixing for 10 minutes, and curing in a muffle furnace at 200°C for 24 hours to obtain modified magnesium aggregate; 25 parts of fused magnesia, 1 part of silicon powder, and 3 parts of Al-Si alloy powder are mixed in a ball mill for 5 minutes, placed in a high-powered mixer, and 60 parts of modified magnesium aggregate, 5 parts of nanocrystalline ZrC coated graphite material and 5 parts of modified phosphate binder are added and mixed for 20 minutes, stirred evenly, discharged, and sealed and packaged in a plastic-lined packaging bag to obtain refractory mud for sliding nozzles.

[0038] Example 2

[0039] Add 6 parts of aluminum hydroxide to a three-necked flask, then add 80 mL of water and start the stirrer, heat in a water bath to 70°C, add 30 parts of phosphoric acid and react for 35 minutes, adjust the temperature to 90°C, add 0.6 parts of boric acid, 0.5 parts of malic acid, 0.3 parts of tartaric acid, and 0.5 parts of triethanolamine and continue to react for 40 minutes, cool to room temperature, and filter to obtain a modified phosphate binder.

[0040] 5 parts of zirconium powder and 12 parts of flake graphite were mixed in an alumina mortar for 15 minutes, and then 30 parts of potassium chloride and sodium chloride (the mass ratio of potassium chloride to sodium chloride is 1:1) pre-mixed for 15 minutes were added and stirred for 15 minutes. The mixture was heated to 1000°C in flowing argon for 3 hours. After the furnace was completely cooled, it was washed three times with a hydrochloric acid solution with a volume concentration of 30%, and then dried in a drying oven at 110°C for 10 hours to obtain nanocrystalline ZrC coated graphite material.

[0041] 70 parts of high-purity magnesia powder and 2 parts of a 50% mass concentration of citric acid-glucosamine hydrochloride mixed aqueous solution (the mass ratio of citric acid to glucosamine hydrochloride is 1:1) are added to a blender and mixed for 3 minutes, followed by adding 3 parts of microsilica powder and mixing for 5 minutes. The mixture is cured in a muffle furnace at 200°C for 24 hours to obtain modified magnesium aggregate. 50 parts of fused magnesia, 5 parts of silicon powder, and 2 parts of Al-Si alloy powder are mixed in a ball mill for 3 minutes, placed in a high-powered mixer, and 35 parts of modified magnesium aggregate, 2 parts of nanocrystalline ZrC-coated graphite material, and 3 parts of modified phosphate binder are added and mixed for 15 minutes. After stirring evenly, the material is discharged and sealed in a plastic-lined packaging bag to obtain refractory mud for sliding nozzles.

[0042] Example 3

[0043] Add 6 parts of aluminum hydroxide to a three-necked flask, then add 80 mL of water and start the stirrer, heat in a water bath to 65°C, add 30 parts of phosphoric acid and react for 30 minutes, adjust the temperature to 90°C, add 0.4 parts of boric acid, 0.9 parts of malic acid, 0.1 parts of tartaric acid, and 0.6 parts of triethanolamine and continue to react for 40 minutes, cool to room temperature, and filter to obtain a modified phosphate binder.

[0044] 5 parts of zirconium powder and 10 parts of flake graphite were mixed in an alumina mortar for 15 minutes, and then 30 parts of potassium chloride and sodium chloride (the mass ratio of potassium chloride to sodium chloride is 1:1) pre-mixed for 15 minutes were added and stirred for 18 minutes. The mixture was heated to 950°C in flowing argon for 4 hours. After the furnace was completely cooled, it was washed four times with a hydrochloric acid solution with a volume concentration of 30%, and then dried in a drying oven at 120°C for 12 hours to obtain a nanocrystalline ZrC coated graphite material.

[0045] 70 parts of high-purity magnesia powder and 10 parts of a 50% mass concentration of citric acid-glucosamine hydrochloride mixed aqueous solution (the mass ratio of citric acid to glucosamine hydrochloride is 1:1) are added to a blender and mixed for 3 minutes, followed by adding 6 parts of microsilica powder and mixing for 10 minutes, and curing in a muffle furnace at 200°C for 24 hours to obtain modified magnesium aggregate; 40 parts of fused magnesia, 3 parts of silicon powder, and 3 parts of Al-Si alloy powder are mixed in a ball mill for 4 minutes, placed in a high-powered mixer, and 40 parts of modified magnesium aggregate, 3 parts of nanocrystalline ZrC coated graphite material and 4 parts of modified phosphate binder are added and mixed for 18 minutes, stirred evenly, discharged, and sealed and packaged in a plastic-lined packaging bag to obtain refractory mud for sliding nozzles.

[0046] Example 4

[0047] Add 6 parts of aluminum hydroxide to a three-necked flask, then add 80 mL of water and start the stirrer. Heat in a water bath to 75°C, add 30 parts of phosphoric acid and react for 35 minutes, then adjust the temperature to 90°C, add 0.6 parts of boric acid, 0.5 parts of malic acid, 0.3 parts of tartaric acid and 0.8 parts of triethanolamine and continue to react for 55 minutes. Cool to room temperature and filter to obtain a modified phosphate binder.

[0048] 5 parts of zirconium powder and 14 parts of flake graphite were mixed in an alumina mortar for 15 minutes, and then 30 parts of potassium chloride and sodium chloride (the mass ratio of potassium chloride to sodium chloride is 1:1) pre-mixed for 15 minutes were added and stirred for 15 minutes. The mixture was heated to 980°C in flowing argon for 3.5 hours. After the furnace was completely cooled, it was washed three times with a hydrochloric acid solution with a volume concentration of 30%, and then dried in a drying oven at 120°C for 11 hours to obtain a nanocrystalline ZrC coated graphite material.

[0049] 85 parts of fused magnesia, 9 parts of silicon powder, and 4 parts of Al-Si alloy powder were mixed in a ball mill for 5 minutes, placed in a strong mixer, and added with 4 parts of nanocrystalline ZrC coated graphite material and 4 parts of modified phosphate binder and mixed for 20 minutes. After stirring evenly, the material was discharged and sealed in a plastic-lined packaging bag to obtain refractory mud for sliding nozzles.

[0050] Example 5

[0051] Add 6 parts of aluminum hydroxide to a three-necked flask, then add 80 mL of water and start the stirrer, heat in a water bath to 65°C, add 30 parts of phosphoric acid and react for 40 minutes, adjust the temperature to 90°C, add 0.5 parts of boric acid, 0.7 parts of malic acid, 0.2 parts of tartaric acid, and 0.8 parts of triethanolamine and continue to react for 50 minutes, cool to room temperature, and filter to obtain a modified phosphate binder.

[0052] 5 parts of zirconium powder and 11 parts of flake graphite were mixed in an alumina mortar for 15 minutes, and then 30 parts of potassium chloride and sodium chloride (the mass ratio of potassium chloride to sodium chloride is 1:1) pre-mixed for 15 minutes were added and stirred for 17 minutes. The mixture was heated to 1000°C in flowing argon for 3 hours. After the furnace was completely cooled, it was washed 5 times with a hydrochloric acid solution with a volume concentration of 30%, and then dried in a drying oven at 110°C for 12 hours to obtain nanocrystalline ZrC coated graphite material.

[0053] 70 parts of high-purity magnesia powder and 5 parts of a 50% mass concentration of citric acid-glucosamine hydrochloride mixed aqueous solution (the mass ratio of citric acid to glucosamine hydrochloride is 1:1) are added to a blender and mixed for 5 minutes, followed by adding 5 parts of microsilica powder and mixing for 10 minutes, and curing in a muffle furnace at 200°C for 24 hours to obtain modified magnesium aggregate; 45 parts of fused magnesia, 2 parts of silicon powder, and 3.5 parts of Al-Si alloy powder are mixed in a ball mill for 4 minutes, placed in a high-powered mixer, and 55 parts of modified magnesium aggregate, 5 parts of nanocrystalline ZrC coated graphite material and 5 parts of modified phosphate binder are added and mixed for 20 minutes, stirred evenly, discharged, and sealed and packaged in a plastic-lined packaging bag to obtain refractory mud for sliding nozzles.

[0054] Example 6

[0055] Add 6 parts of aluminum hydroxide to a three-necked flask, then add 80 mL of water and start the stirrer, heat in a water bath to 70°C, add 30 parts of phosphoric acid and react for 40 minutes, adjust the temperature to 90°C, add 0.4 parts of boric acid, 0.8 parts of malic acid, 0.3 parts of tartaric acid, and 0.7 parts of triethanolamine and continue to react for 60 minutes, cool to room temperature, and filter to obtain a modified phosphate binder.

[0056] 5 parts of zirconium powder and 15 parts of flake graphite were mixed in an alumina mortar for 15 minutes, and then 30 parts of potassium chloride and sodium chloride (the mass ratio of potassium chloride and sodium chloride was 1:1) pre-mixed for 15 minutes were added and stirred for 15 minutes. The mixture was heated to 1000°C in flowing argon for 4 hours. After the furnace was completely cooled, it was washed three times with a hydrochloric acid solution with a volume concentration of 30%, and then dried in a drying oven at 120°C for 10 hours to obtain nanocrystalline ZrC coated graphite material.

[0057] 70 parts of high-purity magnesia powder and 4 parts of a 50% mass concentration of citric acid-glucosamine hydrochloride mixed aqueous solution (the mass ratio of citric acid and glucosamine hydrochloride is 1:1) are added to a blender and mixed for 3 minutes, followed by adding 4 parts of microsilica powder and mixing for 8 minutes, and curing in a muffle furnace at 200°C for 24 hours to obtain modified magnesium aggregate; 50 parts of fused magnesia, 5 parts of silicon powder, and 4 parts of Al-Si alloy powder are mixed in a ball mill for 3 minutes, placed in a high-powered mixer, and 40 parts of modified magnesium aggregate, 3 parts of nanocrystalline ZrC coated graphite material and 4 parts of modified phosphate binder are added and mixed for 20 minutes, stirred evenly, discharged, and sealed and packaged in a plastic-lined packaging bag to obtain refractory mud for sliding nozzles.

[0058] The present invention also carried out comparative examples and related tests.

[0059] Comparative Example 1

[0060] Compared with Example 1, the only difference is that no nanocrystalline ZrC coated graphite material is added, and graphite is directly added. The other preparation methods and components are completely consistent, and refractory clay for sliding nozzle is finally prepared.

[0061] Comparative Example 2

[0062] Compared with Example 1, the only difference is that no modified phosphate binder is added, and sodium hexametaphosphate is directly added as a binder. The other preparation methods and components are completely consistent, and refractory mud for sliding nozzle is finally prepared.

[0063] Comparative Example 3

[0064] Compared with Example 1, the only difference is that no Al-Si alloy powder is added, and the other preparation methods and components are completely consistent, and refractory clay for sliding nozzle is finally prepared.

[0065] Performance testing

[0066] The refractory clay for sliding nozzles prepared in Examples 1 to 6 and Comparative Examples 1 to 3 was used to prepare samples, where water accounted for 15% of the raw material. According to GB / T2997-2015 test method for bulk density, apparent porosity and true porosity of dense shaped refractory products, GB / T3001-2017 test method for flexural strength of refractory materials at room temperature, GB / T5072-2023 test method for compressive strength of refractory materials at room temperature, and GB / T39146-2020 test method for erosion resistance of refractory materials to molten aluminum alloys, the samples obtained in Examples 1 to 6 and Comparative Examples 1 to 3 were subjected to performance tests of bulk density, apparent porosity, flexural strength at room temperature, compressive strength at room temperature, and erosion depth after erosion test. The specific test results are shown in Table 1.

[0067] Table 1

[0068]

[0069] As shown in Table 1, the mechanical strength and slag erosion resistance of the samples prepared using Examples 1 to 6 are better than those of Comparative Examples 1 to 3.

[0070] According to the data analysis in Table 1, compared with Comparative Example 1, the addition of nanocrystalline ZrC-coated graphite material in Example 1 significantly improved the flexural strength and compressive strength at room temperature, and the erosion depth was much smaller than that in Comparative Example 1. Compared with Comparative Example 2, the addition of modified phosphate binder in Example 1 improved the bonding strength of the refractory mortar, making the sample more tightly bonded, increasing the bulk density, and significantly improving the flexural strength and compressive strength. Compared with Comparative Example 3, the addition of Al-Si alloy powder in Example 1 significantly reduced the erosion depth and significantly improved the slag erosion resistance. The absence of modified magnesium aggregate in Example 4 had some impact on the mechanical strength and slag erosion resistance, but was also significantly better than Comparative Examples 1-3.

[0071] Thermal shock resistance testing was conducted on samples fabricated from refractory clay using the sliding nozzles obtained in Examples 1-6 and Comparative Examples 1-3. The test was as follows: Samples calcined at 1500°C for 3 hours were placed in a furnace at 1100°C for 30 minutes and then cooled with a fan for 5 minutes. After three thermal shock cycles, the residual flexural strength of the samples was measured. The residual strength ratio of the samples was calculated according to formula (I). The results are shown in Table 2.

[0072] (I)

[0073] The thermal shock resistance of the samples was evaluated by the residual strength ratio of the samples. The specific calculated results are shown in Table 2.

[0074] Table 2

[0075]

[0076] As can be seen from Table 2, the thermal shock resistance of the samples prepared using Examples 1 to 6 is better than that of Comparative Examples 1 to 3. Among them, compared with Comparative Example 1, the addition of nanocrystalline ZrC coated graphite material in Example 1 enables ZrO2 generated by oxidation of ZrC to effectively fill microcracks during phase change during high-temperature oxidation, significantly improving the thermal shock resistance; the addition of Al-Si alloy powder to form MgAl2O4 also significantly improves the thermal shock resistance; in addition, compared with Comparative Example 2, the addition of modified phosphate binder gives the overall better bonding strength, and the modified binder has better thermal stability, which also improves the thermal shock resistance. The lack of modified magnesium aggregate in Example 4 also affects the thermal shock resistance to a certain extent, but it is also better than Comparative Examples 1 to 3. In summary, the refractory clay for sliding nozzles prepared by the present invention has good comprehensive performance.

[0077] The above is a preferred embodiment of the present invention. Those skilled in the art may make several improvements and modifications without departing from the principles of the present invention. These improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing refractory clay for sliding nozzle, characterized in that: The steps include: S1. Mix aluminum hydroxide, water and phosphoric acid, heat to react, add boric acid, malic acid, tartaric acid and triethanolamine after heating, continue reaction, cool to room temperature, and filter to obtain a modified phosphate binder; S2. Mixing zirconium powder and flake graphite, adding potassium chloride and sodium chloride, stirring, heating to react in an inert gas, cooling, washing, and drying to obtain a nanocrystalline ZrC coated graphite material; S3, ball-milling and mixing fused magnesia, silicon powder, and Al-Si alloy powder, adding nanocrystalline ZrC coated graphite material and modified phosphate binder, and mixing evenly, discharging and packing to obtain refractory mud for sliding nozzle; modified magnesium aggregate is also added when adding nanocrystalline ZrC coated graphite material and modified phosphate binder; The modified magnesium aggregate is prepared by mixing high-purity magnesium sand powder and a citric acid-glucosamine hydrochloride mixed aqueous solution for 3-5 minutes, adding microsilica powder and mixing for 5-10 minutes, and curing at 200° C. for 24 hours.

2. The method for preparing refractory clay for a sliding nozzle according to claim 1, characterized in that: In step S1, the heating reaction time is 30-40 minutes, the temperature is 65-75° C., the temperature after heating is 90° C., and the reaction time is continued for 40-60 minutes.

3. The method for preparing refractory clay for sliding nozzle according to claim 1, characterized in that: The mixing and stirring time in step S2 is 15-20 minutes, the heating reaction temperature is 950-1000° C. and the time is 3-4 hours, and the drying temperature is 110-120° C. and the time is 10-12 hours.

4. The method for preparing refractory clay for sliding nozzle according to claim 1, characterized in that: In step S2, potassium chloride and sodium chloride are premixed for 15 minutes before being added, and the mass ratio of potassium chloride to sodium chloride is 1:1; the inert gas is argon, the washing reagent is a hydrochloric acid solution with a volume concentration of 30%, and the washing number is 3 to 5 times.

5. The method for preparing refractory clay for sliding nozzle according to claim 1, characterized in that: The mass concentration of the citric acid-glucosamine hydrochloride mixed aqueous solution is 50%, and the mass ratio of citric acid to glucosamine hydrochloride is 1:

1.

6. The method for preparing refractory clay for sliding nozzle according to claim 1, characterized in that: In step S3, the fused magnesia, silicon powder, and Al-Si alloy powder are mixed in a ball mill for 3-5 minutes, placed in a strong mixer, and modified magnesium aggregate, nanocrystalline ZrC coated graphite material, and modified phosphate binder are added and mixed for 15-20 minutes. After stirring evenly, the material is discharged and packaged to obtain refractory mud for sliding nozzle.

7. The method for preparing refractory clay for sliding nozzle according to claim 1, characterized in that: In step S3, the discharged material is packaged and sealed in a packaging bag with a plastic lining.

8. A refractory clay for a sliding nozzle, characterized in that: The method for preparing a refractory mortar for a sliding nozzle according to any one of claims 1 to 7 is prepared, comprising the following raw materials in parts by mass: 25 to 85 parts of fused magnesia, 1 to 9 parts of silicon powder, 2 to 4 parts of Al-Si alloy powder, 35 to 60 parts of modified magnesium aggregate, 2 to 5 parts of nanocrystalline ZrC coated graphite material, and 3 to 5 parts of modified phosphate binder; The modified magnesium aggregate includes the following raw materials in parts by mass: 70 parts of high-purity magnesia powder, 2-10 parts of a mixed aqueous solution of citric acid-glucosamine hydrochloride, and 2-10 parts of microsilica powder; the modified phosphate binder includes the following raw materials in parts by mass: 6 parts of aluminum hydroxide, 30 parts of phosphoric acid, 0.4-0.6 parts of boric acid, 0.5-1 parts of malic acid, 0.1-0.3 parts of tartaric acid, and 0.5-1 parts of triethanolamine.

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